[gradsusr] Help in showing the example of using fndlvl(), max() and maxloc()

[See Hai Ooi]

Dear Mr Charles Seman,
 
        I read all the examples in http://grads.iges.org/grads/gadoc/gradfuncfndlvl.html but I still could not get a clear picture out of them. Sorry. 
 
        In my own example, I obtained a maximum wind for each standard level over a specified area.  The highest of all is found to occur around 250 hPa level.  By using fndlvl() in the 2D graphic output, the contour values (100 to 500 at interval of 50) do not make sense. [note: wind expression inside fndlvl() results in contouring while level expression shows "Entire Grid Undefined" in my "composite" gmf.].  Unless the programming structure of this function is known, I think it cannot be utilised for my stated purpose.
 
       I wrote a script (jet3.gs) by using the sorting method to obtain the highest value of all the maximum winds and the corresponding pressure level (The data output values are written in the comment line of the script).  Once I know these values, I can obtain the magnitude and grid coordinates by using max() and maxloc() respectively.  Unfortunately, in my case, the values turned out to be 76.3236 (magnitude) and 12 (pressure level index) respectively instead of 85.7425 and 9 respectively.  I could not figure out my mistakes.  Can you help ?
 
      Thank you very much for your time and untiring effort to assist me.
 
      Best regards.
 
Ooi
 
 
 

 


--- On Wed, 24/3/10, Charles Seman <Charles.Seman at noaa.gov> wrote:


From: Charles Seman <Charles.Seman at noaa.gov>
Subject: Re: [gradsusr] Help in showing the example of using maxloc()
To: "See Hai Ooi" <axl419 at yahoo.com>
Date: Wednesday, 24 March, 2010, 8:01 AM


Ooi,

I did not find the composite figure attached, but the output in "jet.doc" looks like it could be OK:
---





ga-> set lev 1000
LEV set to 1000 1000
ga-> d fndlvl(wind,max(wind,lev=1000,lev=100),lev=1000,lev=100)
MAXing. dim = 2, start = 1, end = 12
Contouring: 100 to 500 interval 50
---

the "Contouring: 100 to 500 interval 50" appears like it could be contouring pressure levels ranging from 100 to 500... if you do "set gxout shaded" before "d fndlvl(...)" you may get a 2D color shaded plot representing a contour map of the pressure levels containing the max wind between 1000 and 100 mb (guessing on the units here)... it appears that the "d fndlvl(lev,max(wind,lev=1000,lev=100),lev=1000,lev=100)" does not work (not sure if it should; please check and compare to Example 3 at http://grads.iges.org/grads/gadoc/gradfuncfndlvl.html)...

Please let me know what you find...

Thanks,
Chuck
 


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